As transistor sizes have decreased, transistor performance has suffered from “short-channel” effects. Some short-channel effects, such as drain-induced barrier lowering, can arise from depletion regions created by the source-drain diffusions. Accordingly, at smaller transistor channel sizes, conventional integrated circuit devices can include transistors with source and drain extensions (SDEs) that extend laterally (with respect to the substrate surface) into channel regions, under a gate electrode. Drain and source extensions are typically formed with “halo” or “tip” ion implantation steps.